I was just part of an intriguing panel titled "Re-Assembly Required: Why Midlife Boomer Women Must Rewrite Their Life Assumptions" that took place at the Aging in America conference in Washington last April. (It was sponsored by the American Society on Aging.) My co-panelists were experts on women’s issues, particularly relationships, caregiving and financial fitness. We each approached these topics from a different perspective, which made for a lively and holistic discussion. I focused my comments on a specific area — the role biology plays in all this — and was encouraged to share them with a larger audience, namely you.

This information isn’t for women only, by the way. It could be even more useful for men. It could help them to understand that some of our supposedly "irrational" behaviors and outbursts have real, and important, underpinnings, both psychological and physiological. It’s not just a case of “forewarned is forearmed,” either. I believe it’s important for all of us to understand the reasons for the many complex changes that occur when we reach midlife — not just changes in our outer lives but the whole cascade of hormonal ones going on inside.

Last year, a friend of mine from New York stepped up to the good-wife plate and accompanied her husband on an ice-fishing trip to Wisconsin, in the dead of winter. She didn’t have a good time (she’s a vegetarian and hates the cold, but that’s another story). On their way home, they had to pass through airport security at Milwaukee County's Mitchell International Airport, which entailed removing many layers of clothing and gear, trying to juggle their carry-on luggage and laptops, taking off their shoes, etc. When my friend got to the other side of the conveyor belt, a sign caught her eye that made her laugh out loud: “Recombobulation Area.”

I love the image of a recombulation area — a place where, after you take everything apart (or it just falls apart), you get to put it all back together again. To me, that’s a perfect metaphor for what life is like for women when we reach a certain … not necessarily age in life, but stage of life, and that's midlife.

The kids are gone, or almost gone, or virtually gone, or maybe you just wish they were gone. If you work outside the home, you’re probably ready to slow down, or maybe speed up or change lanes. And for many of us, that includes our love lives: whether that means finally prioritizing time to find a partner, deepening and strengthening a marriage or relationship that we've been taking for granted, or taking a very hard look at that relationship and deciding whether the good outweighs the bad enough to stick it out.

And darned if it all doesn’t always seem to happen at once.

Although some women are lucky enough to sail through this major transition period unscathed, the vast majority of us find we need to readjust a lot of assumptions. Our panel talked about having to reassess, regroup, reimagine, reinvent, recalibrate, redeem, reassemble, recreate. But why don't we just say recombobulate?

Part of the reason for the need to regroup at this time is societal: get married, have kids in your 20s or early 30s, send them off in your 50s. Careerwise, this is a common time for change — whether for advancement, switching jobs to something more meaningful or finally jumping off the merry-go-round. And for plenty of women of our generation, in this wobbly economy, unexpected or undesired change finds them. So for one reason or another, we find ourselves on new ground.

But underlying all the societal, psychological and physiological urges is something that we’re all aware of — and yet, it's something that most of us probably don’t give enough credence to: our biology. We know that changes come … with the change. Despite the wealth of information out there, we tend to dismiss, or minimize — or not fully acknowledge — the role that our shifting hormones have on everything at this stage of life.

Neuropsychiatrist Louann Brizendine has written a very insightful book called The Female Brain. She knows her stuff, having served on the faculty at the Harvard Medical School in Boston and having founded the Women’s and Teen Girls’ Mood and Hormone Clinic in the San Francisco Bay area. And her stuff is brain science.

Brizendine reminds us that before menopause comes a very bumpy ride called perimenopause, which, biologically speaking, starts around age 43 and can last up to a decade. Perimenopause is marked by erratically cycling estrogen, progesterone and testosterone. These chemicals, which once launched our "urge to merge" and “mommy brains,” are slowing down and producing fluctuating moods and sleep patterns, increased worry and often a loss of interest in sex. What is of interest is daily survival and just staying on the emotional roller coaster and not falling and crashing. Many women, especially in hindsight, describe this period as walking through three or six — or 10 — years of dense fog.

So when menopause hits, for many of us, it comes as blessed relief. The physiological symptoms can be brutal, of course, but by the time we are postmenopausal, usually in our early- to mid-50s, our estrogen levels have dropped off precipitously. A lot is going on here, but what is now steady are our testosterone, progesterone and estrogen’s sister hormone, the cuddly, snuggly, nurturing brain chemical called oxytocin.

With this hormone shift comes an inner calm: We’re less reactive to stress, we’re less emotional, the brain fog (often) lifts, and we see that we’ve actually got a pretty steady, reliable machine: our brain. Our urges are more about staying healthy, embracing new challenges, focusing on what we want and, thanks to the dip in oxytocin, we don’t have the same strong, compulsive need to fix everything and take care of everybody except ourselves. It's not in our heads; it's real.

This hormonal game-change is why so many of the old rules no longer apply, and why a lot of the bases for our old assumptions no longer hold water. What we thought, in our 40s, that we'd want in our 50s and 60s is often rendered irrelevant.

It's a big factor in the spike in divorces that are occurring once the nest is emptied. Statistics show that 65 percent of these divorces are initiated by the wives. No longer worried that it’ll “damage” the kids, or sick of going through the motions in a loveless marriage, or realizing that we’re still waiting to meet the love of our lives … we’re ready for whatever’s next.

The late Eugene Cohen, a psychiatrist, gerontologist and the founder of the Center on Aging, Health and Humanities at George Washington University, found in his extensive research that our brain’s information processing center doesn’t reach its greatest potential until sometime between the ages of 60 and 80. Which means that the best may indeed lie ahead. It's not unusual for women to reach their greatest level of creativity and problem-solving ability and to find themselves happier and more satisfied than they were in their younger days.

True, we’re still the “sandwich generation” that has to care for our aging parents while our kids are either still at home or, in increasing numbers, boomeranging back. Also true: We ourselves are aging — some gracefully, some not so much — and as someone pointed out, we’re the first generation in history where so many can expect to live to a very ripe old age. ﻿So society isn't quite prepared to deal with us and that can produce frustrations — yet at no stage of our lives have we been more prepared to grapple with any glitches that might arise.

Unlike our mothers and grandmothers, midlife isn’t an end point or a place to stop and rest; it truly is a new beginning, or at least it can be if we marshal our resources and create one.

Our hormones are finally tamed, we’ve acquired the skills, knowledge and wisdom to do almost anything we can envision. Many of us have more time on our hands and the means to steer our own ships. We can take comfort in knowing that despite the challenges we've been through — our loves, divorces, careers, kids, illnesses — there’s less to fear than look forward to.

Remember: Our brains are more prepared for this new stage of life than we might be giving it credit for. This isn’t a time to rest on our laurels. It’s time for creative recombobulation.